Most insulation sheets and segments which are used presently either with pipes or duct work have an exterior coating of paper. For example, as shown in copending U.S. patent application Ser. No. 804,066 assigned to the assignee herein, cylindrical insulation segments used with pipes typically comprise an inner, metallized layer, a layer of fiberglass yarn, and an outer, paper layer which is typically a kraft paper. The outer layer frequently includes a scrim laminated between paper layers which produces a textured outer surface to the segment. These cylindrical segments extend along a pipe in an end to end abutting relationship. Also, each segment typically is slit along its length for insertion of the pipe, and a proper flap is provided for covering the slit and for sealing the pipe within the segment. The undersurface of the flap is provided with a strip of a pressure sensitive adhesive to allow it to be secured to the outer paper layer of the segment. The spaces between abutting ends of the segments may be sealed using a tape such as a butt strip tape, having a pressure sensitive adhesive. This tape preferably has an outer paper layer, a middle layer of fiberglass, an inner metallized layer, and a ayer of a pressure sensitive adhesive disposed on the metallized layer, as described in copending U.S. patent application Ser. No. 804,066. The tape is wrapped about the abutting ends of the segments so that one end of the tape overlaps the other end to seal the space between the segments.
Often, it is necessary to apply the strip of adhesive to the undersurface of the flap of the insulation segment at the job site. In this instance, the adhesive is provided on a roll using a double sided release paper having a differential release, as descrbed in U.S. patent application Ser. No. 804,066. Therefore, if the undersurface of the flap has moisture on it at the time of application of the adhesive strip, the adhesive may not bond well to the flap.
In each instance, for both the paper flap and the butt strip tape, the integrity of the seal is a function of the strength of the bond between a pressure sensitive adhesive and a layer of paper, whether it be the tape or the insulation segment. If the tape and flap are sealed in place when the paper layer is dry, and the paper layer never becomes damp through absorption of moisture, the integrity of the seal will be maintained. However, more often than not, especially in new construction, insulation segments are used in basements or areas which are exposed to the weather, where the outer paper layer absorbs moisture from the surrounding environment. Eventually, under such conditions, the paper layer is likely to disintegrate, delaminate or even separate from the fiberglass layer. If this disintegration or delamination occurs, the integrity of the seal between the butt strip tape and the segment or between the flap and the segment may be destroyed. Also, because of the textured outer surface, if inadequate pressure is applied to the flap or the tape, the pressure sensitive adhesive will adhere only to the raised portions of the outer surface, which is less than 25% of the total surface area of the segment. Because of this inadequate bond, "fish-mouthing" is more likely and the bond between the butt strip tape and the outer surface of the segment is less secure. With respect to the flap seal, such delamination or disintegration can allow the flap to rise off the insulation segment to cause what is known as "fish mouthing". "Fish mouthing" can occur as a result of the breakdown between the adhesive strip and the flap or between the adhesive strip and the outer surface of the segment. Such delamination or disintegration can occur over a period of a few weeks in very damp environments, or a period of many months in less damp environments. Eventually, the insulation segments must be removed and replaced if the desired level of protection is to be maintained. "Fish mouthing" is a particular problem on jobs for the U.S. Government, since such "fish mouthing" does not meet specifications for the U.S. Government, and the contractor may be required to return to the site and repair the damage at his own cost.
Some manufacturers of cylindrical insulation segments provide them with an outer layer of plastic such as polyvinylchloride (PVC). Although the PVC does not delaminate, some difficulty may be experienced in securing either the butt strip tape or the flap to the outer surface of the segment if moisture is present. Also, acrylic adhesives are generally used to seal the flap on the segment and to secure the butt strip tape to the segment, and acrylic adhesives do not adhere well to PVC. Any incomplete seal could result in "fish mouthing" of the flap or eventual failure of the seal around the butt strip tape.
Fibrous duct board is often used for insulation of duct work, particularly square or rectanqular ducts. Such duct board is provided in somewhat rigid sheets. This duct board has a structure somewhat similar to that of the pipe insulation segments previously described and generally comprises an outer metallized layer, a middle layer of fiberglass yarns, or mineral wool, and an inner paper layer which is typically a kraft paper. On some duct board products the paper is on the outer surface and the metallized layer is on the inner surface. The fiberglass or mineral wool layer of the duct board is more tightly packed than in the segments, thus providing it with the greater rigidity. The duct board generally is cut to the size of the duct work, and the resulting sheets cover the surfaces of the duct work. Sheets are placed in abutting relationship along each surface, and edges of the sheets on each surface adjoin edges of other sheets disposed on adjacent, perpendicular surfaces of the duct. A pressure sensitive adhesive tape may be used to seal the spaces between abutting and adjoining edges of the duct board. The tape is secured either to the outer surface, either to a metallized layer or to a paper layer. Generally, for adjoining, perpendicular edges of the sheets of duct board, one transverse edge of the tape is applied to an edge of a sheet along one surface, and the tape is then folded along a line parallel to its length so that the other transverse edge of the tape is secured to an edge of a sheet of duct board disposed on an adjoining, perpendicular surface. This fold in the tape occurs across the machine direction of the tape, and therefore the tape resists folding and tends to straighten itself out into its original, generally flat confiquration. As a result, a shear stress results between the tape and the outer surfaces, particularly along the adjoining edges between perpendicular sheets of duct board.
The outer layer of such duct board is susceptible to damage resulting from moisture absorbed from the surrounding environment. If moisture is present either in the paper or on the metallized layer when the adhesive tape is applied, or if such moisture is absorbed by the paper at a later time, the integrity of the seal can be compromised. As with the pipe insulation, the paper layer can disintegrate or separate, thus destroying the bond between the tape and the sheet of duct board. Because of the shear stresses along perpendicular junctions, once the outer layer begins to disintegrate or delaminate, the tape has a tendency to pull free from one or the other of the edges of the perpendicularly disposed sheets of duct board, and this tendency accelerates the delamination or disintegration process. Eventually, the integrity of the seal is destroyed. This process is accelerated if a scrim is laminated into the outer layer and the outer layer is textured, as described for the insulation segments. Again, if the duct work is to be properly insulated, the tape, and often all of the the sheets of duct board must be replaced.
Flexible blanket insulation is also used for insulation of duct work. Such blanket insulation typically is provided in long rolls from which the insulation is cut and wrapped about the duct work. The structure of such blanket insulation has the same structure, in most instances, as the previously described cylindrical insulation segments and duct board, and comprises an outer metalized layer, a middle layer of fiberglass yarns, which are loosely packed to be flexible, and an inner layer which is typically a kraft paper. As described in copending U.S. patent application Ser. No. 905,701, filed Sept. 9, 1986, and assigned to the assignee of the present application, adjacent lateral edges of segments of blanket insulation cut from the roll are sealed to one another by the use of strips of tape to effect a seal about the ducts. Again, the outer paper layer of such blanket insulation is susceptible to damage resulting from moisture absorbed from the surrounding environment or from moisture which is already present in the paper when the tape is applied. If disintegration or delamination of the paper layer occurs, the integrity of the seal could be destroyed if the tape pulls loose.
Again, this process would be accelerated if a scrim is used in the outer layer to provide it with a textured surface. In addition, the tape used to seal together the edges of such blanket insulation is secured in an end to end, overlapping relation. The structure of this tape is substantially identical to that of the butt strip tape previously described, and contains an outer, paper layer. Therefore, if moisture is present in the paper layer of such tape, disintegration or delamination again could occur, thus destroying the seal created by the tape.
In each instance, the replacement of insulation after a very short period of time is very expensive and results in additional building costs. If the insulation is not replaced, the effectiveness of the insulation is significantly reduced, and significant monetary losses result from the escape of heat from the pipes or duct work.
It is an object of this invention to provide a moisture proof surface on insulation segments, sheets and blankets, and on tape used to seal such insulation segments, sheets and blankets at locations where a pressure sensitive adhesive tape is to be applied.
It is also an object of this invention to provide superior adhesive bonding surfaces upon which pressure sensitive adhesive tapes may be applied for sealing pipe insulation segments together.
It is a further object of this invention to provide a superior adhesive bonding surface for the pressure sensitive adhesive layer of the flap on a pipe insulation segment.
It is a further object of the present invention to provide a superior adhesive bonding surface on ends of a butt strip tape used for sealing abutting ends of insulation segments on pipes.
It is a further object of the present invention to provide a superior adhesive bonding surface on the perimeter of sheets of duct board used for insulating ducts to permit secure attachment of pressure sensitive adhesive tapes to the edges of the duct board for sealing abutting and adjoining edges to one another.
It is a further object of the present invention to provide a superior adhesive bonding surface on the lateral edges of rolls of blanket insulation used for insulating ducts to permit secure attachment of pressure sensitive adhesive tapes to the lateral edges of the blanket insulation for sealing abutting and adjoining edges to one another.
It is a further object of the present invention to provide a superior adhesive bonding surface on ends of tape used to seal abutting and adjoining edges of blanket insulation to one another.